The open-source video game emulator component, RetroArch, has added machine translation in version 1.7.8. It is implemented as a button that scans the screen for text. In speech mode, it reads that text aloud to you in whatever target language you select. In image mode, it pauses the game and overlays the translated text. The demo video shows ActRaiser (Quintet, 1990) being translated from Japanese into English using both methods. Other source and target languages are available.
To use this feature, you will need to your own Google API key. Google’s automatic translation service is not free, although (based on Google’s menu) it looks cheap for personal usage. If I am reading it correctly, the service offers 500,000 characters free plus $20 per one million characters over that amount. (It might be more expensive if you use language detection instead of setting it by hand. I have not tried this myself.) It makes sense that RetroArch would not want to pay for every user, so they step aside and let you get your own account with Google.
RetroArch 1.7.8 is available now on their website.